ILHAM TOHTI rarely worries about his personal safety here — at least not at the hands of would-be thieves.

That is because Mr. Tohti, an economics professor and unofficial spokesman for this country’s embattled Uighur minority, frequently has a police escort.

Whether they are looking out for his well-being is another matter.

“You may not see them, especially if I’m out with friends, but they’re there,” said Mr. Tohti, 41, whose ever-present smile seems to convey more sadness than joy.

Just then his cellphone rang. He looked at the number, put his fingers to his lips and whispered “domestic security.” After a quick exchange with his minders, Mr. Tohti hung up and lit yet another cigarette. “They’re very angry with me,” he said sitting in his Beijing apartment. “They told me very clearly that I may be in grave danger.”

These are precarious times for Mr. Tohti, a brazenly outspoken spark plug of a man whose advocacy for China’s Turkic-speaking Muslim Uighurs has landed him on the government’s list of citizens who warrant near-constant surveillance.

Last July, after ethnic bloodletting in the far western region of Xinjiang killed 197 people, the governor appeared on television to accuse Rebiya Kadeer, the exiled Uighur leader, of inciting the violence, much of which involved Uighur mobs bludgeoning Han Chinese migrants in Urumqi, the regional capital. Then he parceled out some of the blame to Mr. Tohti’s Web site, Uighurbiz.net, a lively forum for debate — and a platform for rumormongering, according to the government — before it was blocked by the censors.

The next day, security agents from Beijing took him on what he said they called a “vacation” for three weeks, interrogating him for long periods and warning him to stop publicly criticizing the government’s policies and practices in Xinjiang. The agents later decamped to his living room, although Mr. Tohti declined to describe the experience for fear he might incur their wrath. “Sometimes they were nice to me, but other times they said, ‘We can crush you like an ant,’ ” he said.

It is not clear why they have not crushed him yet. Since the unrest of last summer, the authorities have had little compunction about detaining scores of Uighurs whose whereabouts remain a mystery. In recent weeks, several have been given long prison terms, including three Web masters and a journalist who were convicted for endangering the Chinese state. The longest sentence, 15 years, was handed down to Gheyret Niyaz, a 51-year-old writer who worked for Mr. Tohti’s Web site. Prosecutors say Mr. Niyaz’ greatest crime was speaking to a magazine in Hong Kong.

His fate has weighed heavily on Mr. Tohti and increased his already perilous levels of garrulousness. “They say I’m hyping up his case and that I have to stop talking to the media, but I just can’t help myself,” he said, adding another cigarette butt to an overflowing ashtray.

As one of the few prominent Uighur intellectuals living in China, Mr. Tohti said he felt he had no choice but to speak out against the discrimination and economic inequality he says fuel Uighur resentment, some of which ends up directed at the Han migrants who have been encouraged to move west by the millions. According to the most recent census in 2000, the Han make up 40 percent of Xinjiang’s population, up from less than 5 percent when the Communist Party took power in 1949.

Although the central government recently pledged to invest billions of dollars in Xinjiang, Mr. Tohti says no amount of money can assuage the widespread feeling that the culture and language of the region’s 10 million Uighurs are increasingly threatened by assimilation. It does not help that most government positions and jobs in Xinjiang’s booming oil and gas industries go to the Han.

HE also has harsh words for China’s leaders, who he says pay lip service to the autonomy promised by Chinese law. “I am worried that many of my people might be driven to extremism,” he said.

Such extremism may have been behind an explosion this week that killed seven people in Aksu, a predominantly Uighur city not far from Mr. Tohti’s hometown.

Mr. Tohti knows his frank words have had unintended consequences for those closest to him. His first marriage ended in divorce after his wife, spooked by sirens and jolted by every knock at the door, returned to Xinjiang with their young son. Last year his second wife also fled Beijing, and later she gave birth to their second child.

He admits that the stroke that nearly killed his mother recently may have been brought on by her anxiety over his safety. “She said she would have never allowed me to go to school if she knew I would turn out like this,” he said.

He has more than a dozen relatives in Xinjiang who work in public security, including two brothers who have made repeated trips to Beijing in an effort to persuade Mr. Tohti to tone down his rhetoric, and perhaps ease the pressure from their own superiors.

It is not entirely clear whether his prominence has so far saved him from a worse fate. Wang Lixiong, a well-known writer who studies Xinjiang, said that fame rarely saves high-profile dissidents.

“It could just be that different powers and interests within the government are divided over what to do about him,” Mr. Wang said. “But at some point, a higher authority might decide to step in and do something.”

BORN in Atush, an ancient outpost on the northern branch of the Silk Road, Mr. Tohti says he was a diligent, if slightly distracted, student. His father, educated at Beijing Normal University, died when Mr. Tohti was 2 under circumstances he still does not understand. “I’m afraid to ask my mother, because the subject is too painful for the both of us,” he said.

In the sixth grade, he became acutely aware that the Uighurs and the Han in Atush lived differently. It was the summer of 1980, when a crowd of Uighur children tried to force their way into a movie theater reserved for Han. During a scuffle with Chinese soldiers, a Uighur boy was grievously injured and in the melee that followed, Mr. Tohti joined a rampaging mob that smashed every light bulb and window in sight.

Why light bulbs and windows? “Because these are things the Han had; we lived in primitive dwellings,” he recalled. “I think that’s when many Uighurs opened their eyes and saw what was happening around them.”

For now, he still has his teaching job at Minzu University of China, where his classes are a popular draw among Uighur students. Not surprisingly, his lectures tend to be fiery. They have also become popular keepsakes, recorded and surreptitiously passed among Uighurs around the country.

Students are not the only ones interested in his talks. Not long ago he noticed a surveillance camera mounted in the ceiling of his classroom. Soon afterward, he realized that even when he changed rooms, the cameras followed him. “A coincidence perhaps,” he said with a grin.

Mr. Tohti could probably leave the country and become a Uighur exile, but he refuses to entertain the thought. Only by staying in China, he said, can he help Mr. Niyaz and other jailed Uighurs. He also feels an obligation to his students, many of whom are still unemployed years after graduation. “As a teacher, I feel like I have failed them,” he said.

Then his mood grew even darker.

“If things here don’t change as quickly as I’d like, sooner or later I will be doomed,” he said. “Perhaps I will be sent to hell, but I don’t care because in some ways I am already there.”